Nanoscale Chemical Imaging of Supported Lipid Monolayers using Tip-Enhanced Raman Spectroscopy

Area of Science:

• Surface Science
• Spectroscopy
• Nanotechnology

Background:

• Understanding lipid membrane molecular organization is crucial for biological function.
• Existing techniques lack non-destructive, label-free characterization at the nanoscale.
• Supported lipid monolayers require advanced imaging methods for molecular-level analysis.

Purpose of the Study:

• To demonstrate tip-enhanced Raman spectroscopy (TERS) for probing lipid monolayer organization.
• To correlate lipid monolayer topography with TERS imaging.
• To investigate nanoscale heterogeneity and molecular disorder in lipid membranes.

Main Methods:

• Langmuir-Blodgett (LB) technique for preparing dipalmitoylphosphatidylcholine (DPPC) monolayers on Au (111).
• Tip-enhanced Raman spectroscopy (TERS) for hyperspectral imaging and molecular analysis.
• Correlation of TERS data with sample topography at nanometer resolution.

Main Results:

• High-quality TERS spectra provided direct correlation between lipid monolayer topography and TERS images.
• Hyperspectral TERS imaging identified nanometer-sized holes in the continuous DPPC monolayer.
• TERS imaging revealed reproducible visualization of molecular disorder with 20 nm spatial resolution.

Conclusions:

• TERS is a powerful nanoanalytical tool for investigating lipid membrane molecular organization.
• The study demonstrates TERS's capability for non-destructive, label-free nanoscale characterization.
• LB monolayers, appearing homogeneous, exhibit nanoscale heterogeneity detectable by TERS.